Method and composition of mixed baso&#39; 4 &#39;and srso&#39; 4 &#39;for polishing a photoconductor surface

ABSTRACT

Method for polishing the surface of a photoconductor consisting essentially of amorphous selenium to recover the surface properties of the photoconductor to the original level which has deteriorated by repeated use or aging, and polishing material for such use.

United States Patent [191 Matsuo et al.

[ 1 May 20, 1975 [54] METHOD AND COMPOSITION OF MIXED BASO, AND SRSO, FOR POLISHING A PI-IOTOCONDUCTOR SURFACE [75] Inventors: Kazunori Matsuo, Tokyo; Kohji Suzuki; Katutsohi Endo, both of Yokohama, all of Japan [30] Foreign Application Priority Data Feb. 17, 1972 Japan 47-16724 [52] US. Cl. 252/164; 252/89; 252/163 [51] Int. Cl. C09g 1/02; Cl 1d 7/50 [58] Field of Search 252/89, 163, 164; 51/307 [56] References Cited UNITED STATES PATENTS 2,503,744 4/1950 Kenney et a1 252/89 2,739,129 3/1956 Manchot 3,702,303 11/1972 Clemens et al. 252/163 FOREIGN PATENTS OR APPLICATIONS 937,122 9/1963 United Kingdom 252/163 OTHER PUBLICATIONS Gmelins Handbuch der Anorganischen Chemie, 8th Ed., Barium, System No. 30, p. 388, Verlag Chemie, G.m.b.H.(1932) Berlin. OD 151 G5.

Gmelins Handbuch der Anorganischen Chemie, 8th Ed. Suppl, Barium, System No. 30, pp. 533-534, Verlag Chemie, GmbH 1960) Weinheim/Bergstrasse. OD 151 G5.

Primary ExaminerBenjamin R. Padgett Assistant Examiner-E. A. Miller Attorney, Agent, or Firm-Cooper, Dunham, Clark, Griffin & Moran 57 ABSTRACT Method for polishing the surface of a photoconductor consisting essentially of amorphous selenium to recover the surface properties of the photoconductor to the original level which has deteriorated by repeated use or aging, and polishing material for such use.

5 Claims, N0 Drawings METHOD AND COMPOSITION OF MIXED BASO, AND SRSO FOR POLISHING A PHOTOCONDUCTOR SURFACE BACKGROUND OF THE INVENTION In the xerographic process, amorphous selenium is preferably used as a photoconductor. A layer of amorphous selenium constitutes a photoconductive layer for xerographic plates. The layer of amorphous selenium is formed on a conductive substrate such as a copper or aluminium plate by vacuum evaporation. The xerographic process consists of the steps of:

1. Charging a surface of photoconductive layer by a corona discharge,

2. forming an electrostatic latent image on the photoconductive layer by image-wise exposure to light,

3. electrically precipitating toners (in powder form) on the latent image to form visible image,

4. transferring the visible toner image to a transfer medium such as a paper sheet, and

5. affixing the transferred toner image to the paper sheet by fusing.

The toners are powders generally made of a mixture of carbon black and synthetic resin such as a styrenebutadiene copolymer. Accordingly, the synthetic resin is melted by fusing to affix the toners to the paper sheet. All of this is well known to those skilled in the art. A DC. voltage of 6kV (or kV) is applied in the corona discharge and generally, an acceptance potential of about 750V (or about 700V) is obtained. The acceptance potential which may be obtained is reduced to the extent of about 660V (or 600V) by repeatedly using the photoconductive layer, for example, 10 thousands times. This reduction of the acceptance potential is caused by the following factors:

1. the attachment of toners or dust (in the air) to the surface of the photoconductor,

2. the roughness of the surface of the layer resulting from the attachment of the dust, and

3. the change in quality of the surface attributed to aging.

Accordingly, in order to recover the deteriorated photoconductor to obtain the original acceptance potential, it is required to clean or polish the surface of the photoconductor. For this purpose, various polishing (or cleaning) materials or methods have been proposed. For instance, there are disclosed cubic salts e.g. NaCl or NH Cl in U.S. Pat. No. 2,484,782, BaSO, metaphosphate salts in U.S. Pat. No. 2,772,991, and kieselguhr and etherified cellulose in U.S. Pat. No. 3,100,726. Further, it is well known to those skilled in the art that a dispersion of Ce O in hydrocarbon is useful as a polishing material.

The use of solvents by which a toner film formed on the surface of the photoconductor is removed is also known. One such solvent is isopropyl alcohol.

However, these procedures to polish or clean the surface of the photoconductor have not been completely satisfactory.

It is an object of the present invention to provide an improved polishing material and method for use in polishing a surface of amorphous selenium photoconductors.

SUMMARY OF THE INVENTION The present invention relates to polishing materials and methods for polishing the surface of amorphous selenium photoconductors.

As previously stated, the surface of photoconductive amorphous selenium, which is used in the xerographic process, will deteriorate in quality by repetitive use. It has been found that:

l. in order to recover the deteriorated surface, it is effective and efficient to polish the surface with strontium sulfate (SrSO or barium sulfate (BaSO powders, or preferably a mixture thereof,

and

2. it is most effective and efficient to polish the surface with absorbent cotton (or cotton wool) holding a suspension of a mixture of SrSO and BaSO, in an organic solvent such as isopropyl alcohol.

Photoconductive layers used in this invention may be prepared as follows: the photoconductive'layer i.e. an amorphous selenium layer is formed on a conductive support (for example, an aluminum drum having a diameter of 17cm) by depositing a thin layer (about 50p. thick) of selenium by vacuum evaporation. The dark resistivity of a selenium layer thus formed is lOQ.cm.

Toners used in this invention may be made as follows: a mixture of one part by weight of carbon black and ten parts by weight of butadiene-styrene copolymer is heated to a temperature of about 200C. After cooling, the mixture is finely divided to powders having a particle size of from lg. to 20a.

Using the photoconductive layer and the toners as prepared above, xerographic copying process comprising (1) charging by corona discharge of +6kV or +5kV, (2) image-wise exposure to light, (3) development, and (4) transferring was repeated about ten to twenty thousands times.

The deteriorated photoconductive layer thus obtained was polished with absorbent cotton holding each of the polishing materials mentioned below having particle size of 0.1;1. to 30/.L. The polishing ability of each of the polishing materials was compared and evaluated, and it was found that strontium sulfate and barium sulfate are most effective.

The polishing materials are as follows: calcium carbonate (CaCO cerium oxide (Ce O Zirconium oxide (ZrO magnesium oxide (MgO), titanium oxide (TiO silicon oxide (SiO chromium oxide (Cr O aluminum silicate Al SiO magnesium silicate (Mg SiO calcium silicate (Ca SiO aluminum sulfate (Al (SO.,) calcium sulfate (CaSO strontium sulfate (SrSO barium sulfate (BaSO magnesium sulfate (MgSO zinc sulfide (ZnS), 'Zinc chloride (ZnC1 and kieselguhr.

The above-cited compounds are chemical reagents which are readily available commercially.

SrSO or BaSO solely may be used individually as a polishing materials, but a mixture of SrSO and BaSO, in the ratio of 15:1 to 1:15 (by weight) is more effective. However, a suspension of said mixture in methyl alcohol, ethyl alcohol, propyl alcohol or isopropyl alcohol is most effective and efficient.

The characteristics of SrSO, and BaSO, are as shown below: A

potential The polishing material of the present invention is' used in the manner as illustrated below:

After toners attached to the photoconductive layer have been removed by a light brushing of the layer with EMBODIMENTS The following nonlimiting examples are given by way of illustration only.

EXAMPLE 1 Polishing materials No. l No. 6 were prepared from the following ingredients:

Parts by weight No. l SrSO (only) No. 2 BaSO, (only) No. 3 SrSO, l B2150 4 No. 4 SrSO, l B1150 l lsopropyl alcohol 10 No. 5 SrSO l BaSO l0 No. 6 SrSO, l0 BaSO, l Ethyl alcohol 10 700-710V by corona discharge of +6kV or +5kV, respectively.

2. After copying process was repeated 15,000 20,000 times with toners made of carbon black and soft cotton, the surface is polished by wiping several 5 butadiene-styrene copolymer, a reduced acce times with absorbent cotton holding a dispersion of tance tential obt i d b corona discharge of SrSO or BaSO in isopropyl alcohol. As the surface is +6kV or +5kV w b v d, left Stan ing for to Seconds aftef Polishing, 3. After the surface of the photoconductive layer was P p) alcohol evaporates and browmsh Powders respectively polished with polishing materials No. main on the surface. The toner powders can easily be 10 1 N 6 a recovered acceptance potential bremoved y W p the Surface with soft Cotton, and tained by corona discharge was measured, and apthen the surface may be wiped with absorbent cotton pearance f the Surface was observed holding p py alcohol, 1f dislred- The data and the results are shown in the table below:

Polishing material No I No. 2 No. 3 No. 4 No. 5 No. 6

Corona discharge 6 6 6 6 5 5 Initial acceptance 750 760 750 750 700 7 l 0 potential Number of repetition of 20,000 20,000 20,000 20,000 15,000 15,000 copying process Reduced acceptance 650 640 660 660 600 600 potential Recovered acceptance potential 720 750 730 750 670 650 (after polishing) Appearence of slightly very very the surface of marred smooth smooth smooth smooth smooth photoconductor and scratched DESCRIPTION OF THE PREFERRED As is seen from the above-mentioned data and resuits, the polishing materials No. 3 No. 6 made of a mixture of SrSO and BaSO are preferred.

EXAMPLE 2 An amorphous selenium photoconductor was allowed to stand for 6 months in the air.

The initial acceptance potential and reduced acceptance potential (after 6 months) obtained were respectively 750V and 650V by corona discharge of 6kV. After the deteriorated surface of photoconductor was polished with polishing materials No. 3, No. 4 and N0. 5 of Example 1, a recovered acceptance potential was measured.

The polishing materials No. 3, No. 4 and No. 5 gave respectively recovered acceptance potentials of 740V, 750V and 720V.

The polishing material of this invention may also be used in polishing photoconductive surfaces consisting of amorphous selenium containing a small amount of other elements such as tellurium, arsenic, sulfur or thallium.

We claim:

1. Method for polishing a surface of photoconductor consisting essentially of amorphous selenium with polishing material, said polishing material comprising a mixture of strontium sulfate and barium sulfate.

amorphous selenium, comprising a mixture of strontium sulfate and barium sulfate in the ratio of from 15:1 to 1:15 parts by weight, the particle size of the strontium sulfate and barium sulfate being from 0.1 p. to 30 u. v 5. Polishing material of claim 4 suspended in an alkanol containing from 1 to 3 carbon atoms. 

1. METHOD FOR POLISHING A SURFACE OF PHOTOCONDUCTOR CONSISTING ESSENTIALLY OF AMORPHOUS SELENIUM WITH POLISHING MATERIAL, SAID POLISHING MATERIAL COMPRISING A MIXTURE OF STRONTIUM SULFATE AND BARIUM SULFATE.
 2. Method according to claim 1 wherein said polishing material is a mixture of strontium sulfate and barium sulfate in the ratio of from 15:1 to 1:15 parts by weight.
 3. Method according to claim 2 wherein particle sizes of strontium sulfate and barium sulfate are from 0.1 Mu to 30 Mu .
 4. POLISHING MATERIALS FOR USE WITH PHOTOCONDUCTIVE AMORPHOUS SELENIUM, COMPRISING A MIXTURE OF STRONTIUM SULFATE AND BARIUM SULFATE IN THE RATIO OF FROM 15:1 TO 1:15 PARTS BY WEIGHT, THE PARTICLE SIZE OF THE STRONTIUM SULFATE AND BARIUM SULFATE BEING FROM 0.1 U T 30 U.
 5. Polishing material of claim 4 suspended in an alkanol containing from 1 to 3 carbon atoms. 